1. Field of the Invention
The invention relates to a mixture charged gas engine, and to a method for compensating for volumetric efficiency deviations.
2. Description of the Related Art
Gas engines of the type discussed herein are known. It is hereby differentiated between pressurized or air charged gas engines on the one hand and mixture charged gas engines on the other hand. Both types of gas engines comprise at least one cylinder, wherein a combustion chamber, delimited by a cylinder head, a cylinder wall and a piston that can be moved in the cylinder is arranged in the at least one cylinder. The cylinder wall can herein also be the wall of a cylinder liner. Depending on the volume of the combustion chamber or, respectively, the diameter of the cylinder, the combustion chamber in a gas engine is typically divided into a main combustion chamber and at least one pre-chamber that is fluidically connected with the main combustion chamber via at least one opening, a so-called firing channel. A volume of a mixture that is reliably ignitable via a spark plug is admitted into the pre-chamber. During a combustion cycle of the cylinder, the mixture is initially ignited in the pre-chamber with the assistance of the spark plug. The ignition energy of the ignition spark of the spark plug is hereby intensified by the energy of the mixture volume that is ignited in the pre-chamber. The burning mixture shoots through the firing channels into the main combustion chamber, where a reliable and complete combustion is triggered due to the increased ignition energy. An air-charged gas engine is known from DE 10 2004 016 260 A1 wherein compressed air is supplied into the main combustion chamber via an inlet valve during an intake stroke of the piston. A separate combustion gas supply is provided for a pre-chamber, through which combustion gas is admitted into the pre-chamber. In one compression stroke of the piston, the drawn-in compressed air is pressed into the pre-chamber where it is mixed with the combustion gas. Subsequent ignition of the mixture occurs in the pre-chamber and finally—as already described—combustion occurs in the combustion cycle of the cylinder. An air compressed gas engine of this type is comparatively complicated and therefore expensive. In contrast, mixture charged gas engines are of comparatively simple design. Here, a turbo charger takes in an air-/combustion gas mixture through a gas mixer and compresses it. During an intake stroke of the piston, the compressed air-/combustion gas mixture is supplied via an inlet valve. It is further compressed in a compression stroke of the piston and pressed into the pre-chamber via the firing channels. Subsequently—as already described—ignition and combustion of the mixture occurs. Whereas air-charged gas engines have flushed pre-chambers with separate combustion gas supply via which the combustion gas is admitted into the pre-chamber, mixture charged gas engines are equipped with unflushed pre-chambers without their own combustion gas supply into which the air-/combustion gas mixture is supplied via the firing channels.
During the intake stroke of the piston, the air-/combustion gas mixture in a mixture charged gas engine is intermixed and homogenized as ideally as possible in order to achieve an as homogeneous and favorable cylinder charge as possible. At the same time, a volume of the mixture-line and an exhaust gas line, a mixture pressure in the mixture line and an exhaust gas pressure in the exhaust gas line, as well as an opening in the inlet as well as in the outlet valves of the cylinders are coordinated in such a way that an as high as possible volumetric efficiency—in other words an as favorable ratio as possible—is achieved after completion of charge changing of a reload actually contained in the cylinder relative to a theoretically possible maximum charge. For intermixing and homogenizing of the air-/combustion gas mixture, a spiral channel is typically provided in the cylinder head.
If the mixture charged gas engine includes more than one cylinder and/or more than one cylinder bank, cylinder individual or cylinder bank individual volumetric efficiency deviations will inevitably occur. If the engine is, for example, designed as a V-engine, two rows of cylinders that are arranged parallel to each other are arranged relative to each other in the shape of a V. The one row of cylinders arranged parallel to each other is typically referred to as “A-bank”; the row of parallel cylinders that is arranged at an angle relative to this row is typically referred to as “B-bank”. It is evident thereby that typically the spiral channel that is provided in the cylinder heads for intermixing and homogenization of the air-/combustion gas mixture is optimized for the geometric conditions of the A-bank, whereby however, for cost reasons, it can also be provided in the same manner in the B-bank. In this case, a lower volumetric efficiency occurs already for the cylinders in the B-bank than for the cylinders in the A-bank. Moreover, differences in the volume in the mixture line and in the exhaust gas line, fluctuations in the mixture pressure and in the exhaust gas pressure, an ignition sequence of the cylinders as well as flow-technological correlations can lead to cylinder individual or cylinder bank individual deviations in the volumetric efficiency due to stationary as well as transient effects.
What is needed in the art is a mixture charged gas engine that can overcome some of the previously described disadvantages.